Katsushi Kobayashi

An explicit router feedback framework for high bandwidth-delay product networks

Links with high bandwidth ranging from 1 to 10Gbps are increasingly in use worldwide. Congestion control with the positive use of router feedback that explicitly indicates network conditions is a promising way to address the performance issues of congestion control especially in such high-speed networks. In this paper, we propose SIRENS, a scalable, robust, and flexible fine-grained explicit router feedback framework. SIRENS is a per-hop and in-band notification scheme where each router captures a snapshot of the various kinds of downstream link status along the IP-level path from a sender to a receiver and notifies the receiver of the status. The receiver can find out the overall path status by assembling all the cumulative notifications that indicate the status in each of the single hops and by feedback can share this information with the sender. Such per-hop information is needed by end-hosts if we are to flexibly design novel congestion control mechanisms or to significantly improve the performance of conventional forms of congestion control. We show the feasibility of SIRENS in terms of router processing overhead through the development and evaluation of a network-processor-based high-performance network emulator. As a typical application of SIRENS, we show the configuration of TCP Limited Slow-Start. Through the implementation and evaluation, we have made sure that a sender can shift from the slow-start phase to the congestion avoidance phase without any packet drop, and can achieve more effective bandwidth utilization.

Flexible arrays of inexpensive network (FAIN): toward global parallelism in the internet to satisfy future traffic growth

In this study, we present the flexible arrays of inexpensive network (FAIN) architecture: it can be used to maximize parallelism in network systems in order to satisfy future Internet traffic growth. Although the parallel-in-global approach used in FAIN overcomes a constraints of serial interfaces, the performance of applications with s small stream can be preserved. FAIN provides thousand of isolated virtualized slices, and enables incremental extensions in the capacity of router systems. FAIN also provides multiple level subscriber differentiation, and power consumption optimization according to the traffic.

Quasi-particle energy band structure and core-electron transition energy calculation for two-dimensional hexagonal boron nitride

Abstract An ab initio quasi-particle energy band structure for hexagonal boron nitride is calculated with the one-particle many-body Green function approach including core-level electrons. Both the valence and conduction band widths are calculated to be narrow compared with the Hartree-Fock (HF) band width, and the core electron levels are shifted upward from the HF results. The calculated energy gaps from the boron 1s level to several upper valence and conduction levels are found to be close to the results of ESCA, photoemission and electron energy loss experiments.

LAWIN: A Latency-AWare InterNet architecture for latency support on best-effort networks

While strict latency restrictions are imposed on network applications, current best-effort Internet architecture entirely lacks this support. In this paper, we propose a “Latency AWare InterNet” (LAWIN) architecture that supports various latency requirements while retaining the best-effort service model. In the LAWIN architecture, applications specify their desired network latency limits, or deadlines, into all packets, and routers schedule these packets according to their deadlines. To this end, we propose two earliest-deadline-first (EDF)-based packet schedulers. The first imposes the same packet loss rate on all applications regardless of the latency specified by each, and provides rough flow-rate fairness. The second scheduler imposes a biased packet loss probability. The biased scheduler also provides an efficient latency and bandwidth trading mechanism for application settings, which motivates applications to set optimal latencies in order to improve efficiency.

THE UNRESTRICTED HARTREE-FOCK SELF CONSISTENT FIELD CALCULATION FOR SPIN DENSITY WAVE STATE IN METALLIC CARBON NANOTUBE

The possibility of a spin density wave (SDW) state in a metallic carbon nanotube (CN) and its electronic properties are investigated within the Hartree-Fock self consistent field (SCF) energy-band calculation. Two kinds of spatial SDW states are assumed in this study. Each assumed SDW on the wave function is constructed with the degenerate π orbital in the metallic CN system. The results calculated for the one SDW model of CN always have a relative stability (∼ 0.1 eV/cell) in SCF total energy compared with the original model in which no SDW is assumed. All the results calculated for another SDW model are completely equal to the original one. Moreover, in the energy dispersion of the former stable SDW model, the degenerate π level found in the original model disappears and the band gap (3-5 eV) occurs around at the Fermi level. The energetic stability and the band gap are also found in the π-electron band calculation within the Hubbard Hamiltonian.

Exploiting fine-grained explicit router feedback towards high-performance transport protocols

The positive use of router feedback that explicitly indicates internal network conditions is a promising way to address the performance issues of congestion control in highspeed networks. In this paper, we propose SIRENS, a scalable, robust, and flexible fine-grained explicit router feedback framework where each receiver can find out the overall path status by assembling all the cumulative router feedback that indicate the status in the single hop. Such per-hop information is needed by end-hosts to design novel congestion control mechanisms or to significantly enhance the performance of traditional forms of congestion control in specific situations. As one typical application of SIRENS, we examine the optimization of TCP limited slow-start. Through the implementation and evaluation, we have made sure that a sender can shift from a slow start phase to a congestion avoidance phase without any packet drop, and can achieve more effective bandwidth utilization. We also examine multi-rate multicast congestion control as another application and evaluate the performance through simulations

The black phosphorus band structure calculation with a semi-empirical crystal orbital approach

Abstract The energy band structure of black phosphorus is calculated with the Hartree—Fock self-consistent-field crystal-orbital method using the CNDO/2 approximation. The band gap is found at the point in the first Brillouin zone that corresponds to the direction perpendicular to the phosphorus layer. The lowest-order correction of Koopmans theorem is estimated with the diagonal approximation of the k space-extended one-particle Green function method. As a result, the drastic reduction of band gap from 7.85 to 2.20 eV is found.